The invention relates to a pneumatic emergency shutdown system and particularly to a pneumatic emergency shutdown system for a liquefied gas supply arrangement in which liquefied gas is supplied between a first tank and a second tank such as a delivering truck and a receiving vessel and/or a receiving terminal or liquefied gas storage tank. The system is a pneumatic safety arrangement for preventing human errors occurring in the loading and unloading liquefied gas in particularly liquefied natural gas (“LNG”). The system is automated.
An emergency shutdown system is typically known as an emergency shutdown valve and an associated valve actuator, i.e. a valve that stops flow in an emergency. An emergency shutdown system is a requirement for the carriage of liquefied gases.
Growth of the truck deliveries of liquefied gas, for example LNG, has brought up many safety issues and there is a need for an automated ESD-link between the truck and the receiving vessel. Previously there has been no other link between the truck and the receiving vessel other than a human link. In case of an emergency, when the emergency shutdown system is activated in the receiving vessel, there is no existing automated system that transfers the emergency shutdown system signal to the delivering truck and launches the truck's own emergency shutdown system. The way to inform the driver about the activated emergency shutdown system in the receiving vessel insist the action from the user which leads to a possibility of the human error being present.
Publication U.S. Pat. No. 6,622,758 discloses a pressure sensing line that detects the cryogenic liquid pressure at the off-loading port of a dispensing station. The off-loading port connects the tank of a delivery vehicle. Each of the dispensing station valves is connectable to the off-loading port. Each valve is kept closed, if the cryogenic liquid pressure is below a preset level. The invention disclosed in the publication prevents cryogenic liquid spill in case of drive offs, controller error or failure in dispensing station valves. So the publication discloses a system for dispensing LNG from a delivery truck to a storage tank at a dispensing station. A device is disclosed which has an emergency shutdown valve which can be activated with a pneumatic signal from the far end of the supplying pipe closing the valve at the delivery truck. In the publication the pneumatic signal controlling the valve is activated simply by detecting a drop in pressure in the supplying pipe which is not a signal of an ESD system of the receiving party. Also the receiving party is a storage tank which does not have an ESD system.
The present invention eliminates the human error possibility from the delivery chain between the delivering and receiving vessels. It also minors the danger zones needed for unloading/loading the liquefied gas, for example LNG, because the automated system diminishes the amount of released/leaked liquefied gas in case of total emergency.